Switching Performance Comparison of the SiC JFET and the SiC JFET/Si MOSFET Cascode Configuration

Silicon Carbide (SiC) devices are becoming increasingly available in the market due to the fact that its manufacturing process is more mature. Many are their advantages with respect to the silicon (Si) devices as, for example, higher blocking capability, lower conduction voltage drop and faster transitions, which makes them more suitable for high-power and high-frequency converters. The purpose of this paper is to study the switching behavior of the two configurations more-widely studied in the literature using SiC devices: the normally-on SiC JFET and the cascode using a normally-on SiC JFET and a low-voltage Si MOSFET. A comparison regarding the turn-on and turn-off losses of both configurations is detailed and the results are verified with the experimental efficiency results obtained in a boost converter operating in both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). Furthermore, a special attention will be focused on the switching behavior of the cascode configuration and the effect of its low-voltage MOSFET is analyzed and different Si devices are compared. The study carried out will confirm that the overall switching losses of the JFET are lower, making it more suitable to operate in CCM in terms of the global efficiency of the converter. Nevertheless, the lowest turn-off losses of the cascode highlight this device as the most appropriate one for DCM when ZVS is achieved at the turn-on of the main switch. Finally, all theoretical results have been verified by an experimental 600W boost converter.